214 J. D. Dana — History of the Changes in Kilauea. 



contrary, it kept its flat surface, thus showing that it probably 

 followed down a liquid mass, that of the subsiding conduit 

 lavas. 



But it is probable that the conduit had then, and has still, a 

 larger area than that of Kilauea 



At the eruption of March, 1886, when the emptying of 

 Halema'uma'u and its bordering lake, at the south end of 

 Kilauea, was all the visible evidence of discharge, the Solfatara 

 at the north end, two and a half miles from Halema'uma'u, 

 showed sympathy with the movement. For the escape of 

 vapors from its fissures suddenly ceased, as if the source of the 

 hot vapors had participated in the ebb, while a few hours 

 before the discharge the vapors were unusually hot, so as to 

 prevent the use of the bath-house (xxxiv, 351). Thus, even 

 now, during a comparatively small discharge, we have evidence 

 that the two distant extremities of the crater are underlaid by 

 inter-communicating liquid lava. Mr. Brigham speaks of 

 hearing, in 1880 (xxxiv, 27) when at the vapor-bath house in 

 the Solfatara, sounds from below, " rumbling and hard noises 

 totally unlike the soft hissing or sputtering of steam," a fact 

 that seems to favor the above conclusion. Further, through 

 all known time, as now, several of the fissures in the Solfatara 

 region have discharged, besides steam, sulphurous acid freely, 

 and this can come only from liquid lavas. 



The summit of the conduit must, therefore, be even larger 

 than all Kilauea. To this may perhaps be added the bor- 

 dering region of fissures and abrupt subsidences ; for subsi- 

 dences or down-plunges indicate undermining, and under- 

 mining here means the removal of liquid material from beneath. 

 With this addition to the limits, the width is 16,000 feet and 

 the length as much, phis a mile or more to the southwest, 

 where the fissures of 1868 if not also of earlier date, are giving 

 off hot vapors abundantly. 



But while this may be the area of the upper extremity of 

 the conduit, the top surface is not a level plane, as the condi- 

 tion of the region above it indicates. A small part of it at all 

 times (with short exceptions after an eruption) has extended 

 up to the surface in Halema'uma'u, and occasionally in other 

 lava-lakes during times of special activity ; for each such lake, 

 however small, must have its separate conduit reaching down 

 to the general liquid mass and giving upward passage to the 

 working vapors. We learn hence that whatever the number 

 of these conduits, they may act independently, that is over- 

 flow, and rise and fall in level, because the size is very small 

 compared with that of the reservoir from which they rise. 



